The embodiments described herein relate generally to combustion systems, and more specifically, to methods and systems to facilitate optimal mixing of liquid and gaseous fuels with oxidizer in a turbine combustor, such as in a gas turbine engines or liquid fueled aero-engines.
During combustion of natural gas and liquid fuels, pollutants such as, but not limited to, carbon monoxide (“CO”), unburned hydrocarbons (“UHC”), and nitrogen oxides (“NOx”) emissions may be formed and emitted into an ambient atmosphere. CO and UHC are generally formed during combustion conditions with lower temperatures and/or conditions with an insufficient time to complete a reaction. In contrast, NOx is generally formed under higher temperatures. At least some pollutant emission sources include devices such as, but not limited to, industrial boilers and furnaces, larger utility boilers and furnaces, liquid fueled aero-engines, gas turbine engines, steam generators, and other combustion systems. Because of stringent emission control standards, it is desirable to control NOx emissions by suppressing the formation of NOx emissions.
To increase the operating efficiency, at least some known turbine engines, may operate with increased combustion temperatures. Generally, in at least some of such known engines, engine efficiency increases as combustion temperatures increase. However, as previously alluded to, operating known turbine engines with higher temperatures may also increase the generation of polluting emissions, such as oxides of nitrogen (NOx). In an attempt to reduce the generation of such emissions, at least some known turbine engines include improved combustion system designs. For example, many combustion systems may use premixing technology that includes fuel injection nozzles or micro-mixers that mix substances, such as diluents, gases, and/or air with fuel to generate a fuel mixture for combustion. Future NOx emissions targets appear unattainable with current injectors without design changes.
Other known combustor systems implement lean-premixed combustion concepts and attempt to reduce NOx emissions by premixing a lean combination of fuel and air prior to channeling the mixture into a combustion zone defined within a combustion liner. In this type of combustor system, a primary fuel-air premixture is generally introduced within the combustion liner at an upstream end of the combustor and a secondary fuel-air premixture may be introduced towards a downstream exhaust end of the combustor.
It should be appreciated that the above-described combustor systems include fuel injectors that typically rely on a jet-in, cross flow type of injection from limited number of orifices along one axial plane on a centerbody of the fuel injector. In many instances, the orifice counts are restricted to achieve sufficient penetration to meet mixing and efficiency targets. This means, higher supply pressure for the fuel and a resultant fuel wall wetting due to injection being from the centerbody. In addition, these conventional fuel injectors typically have a low operability range owing to variability in fuel jet penetration. In addition, these known injectors will have higher auto-ignition risks when operating at high operating pressure ratios (OPRs).
As a result, intricate assembly methods are often required to meet specified performance criteria. As such, a need exists for an advanced fuel injector, preferably for use in an aero-engine application that facilitates optimal mixing of liquid and/or gaseous fuels with oxidizer in a turbine combustor, resulting in reduced NOx emissions.